Algae are increasingly recognized as a renewable source of biofuel, but also have many other commercially valuable applications, such as pharmaceuticals, animal/fish feed, and fertilizers. However, there remain many problems in the large-scale production of algae, which hinder their economic competitiveness with other biofuel crops.
Algae are typically small in size (2-30 μm) and are cultivated in relatively dilute concentrations (generally less than 0.5 g dry biomass L-1), which makes harvesting and dewatering algal cultures particularly problematic and expensive. External inputs, such as nutrients, freshwater, and gases, also add a substantial environmental and economic burden. Wastewater, on the other hand, is a free source of nutrients, water, and carbon dioxide and, if utilized in algae production, could improve the economics and environmental footprint of large-scale algae production. However, utilizing wastewater may increase the chances of introducing predators, grazers, and invasive species to an algal culture, which can lead to algal culture collapse. As a case in point, open raceway ponds are easily contaminated by environmental contaminants (e.g., bacteria, fungi, and rotifers). Although synthetic growth media can be sterilized before it is added to a closed algal culture, this can add substantial cost to production.
From the above discussion, it can be appreciated that it would be desirable to have an alternative system and method with which algae can be cultivated, harvested, and dewatered.